A quartic approximation of the nonlinear inundation effect of Morison-type wave loading is proposed. Using Taylor series expansion, the inundation force due to varying free water surface can be represented by a 'concentrated load', acting on the structure at the mean water level, of which the drag component can be modelled by a polynomial of the fourth order. Polynomial coefficients are obtained using the least squares approximation method, and they are shown to depend upon the wave conditions. However, simple expressions for the polynomial coefficients are recommended based on a numerical study showing that the coefficients are mainly functions of the standard deviation of water particle velocity at the mean water level.

Source Title:

Proceedings of the International Offshore and Polar Engineering Conference